I am not considering "the demand factor", or the 80% rule. I am talking pure concept. 200amps@240V is the same as 400amps@120V. Basic math can prove this, 240Vx200amps = 48000W, 120Vx400amps = 48000W.
What I am saying, is that a panel rated for 200amps@240v, can have 20 fully loaded 20amp@120V...